The present invention relates to compounds for grinding and polishing, such as those used in the dental industry.
Pumice (crushed volcanic rock) is widely used by dentists and dental technicians to abrade, grind, smooth, buff and finish dental acrylics, gold, metals, chrome-cobalt alloys and porcelain and other materials associated with prosthetic and orthodontic dental appliances. In these applications, pumice has generally been used by adding pumice powder to a shallow pan which lies underneath an arbor and polishing wheel of a lathe. Water is then added to the pumice and mixed together to form a polishing medium with the consistency of very fine, wet beach sand. The operator activates the lathe, thus spinning the polishing wheel, and scoops this wet pumice from the pan by hand and applies it to either the polishing wheel, the area of the prosthetic appliance to be polished, or both. The dental appliance is then forced onto the underside of the wheel, while applying an appropriate amount of pressure, to remove deep gouges and rough surfaces created by dental rotary instruments in the fabrication and/or adjustment of the appliance. The amount of time necessary to bring the acrylic surface to one of relative smoothness depends mainly on how abraded the surface is, the volume of area to be polished and the grit size of the pumice used.
Pumice is generally supplied as a crushed powder in which an aqueous liquid, mainly water, is added to wet the powder in order to produce a usable mixture. This wet pumice mixture is generally contained with in a shallow rectangular pan, encased in a splash hood, which lies below a polishing wheel fixed to an arbor connected to a polishing lathe. This wet pumice is then applied to a prosthetic or orthodontic dental appliance or to the revolving wheel of the lathe, and the appliance forced against the wheel to reduce the abraded surfaces of the appliance created mainly by dental rotary instruments during the fabricating and/or adjusting of the appliance. This abrasion of the appliance surface, by the rotary instruments as well as the pumice granules potentially releases microorganisms present on or below the surface of the appliance. This contamination is transferred into the bulk pumice supply below the wheel as well as becomes imbedded in the fibers of the polishing wheel. This microbial contamination can potentially be transmitted to all future appliance cases, the operator and possibly even the patient, presenting a cross-contamination hazard that needs to be rectified.
Throughout the dental community, recommendations have been put forth to enable dentists and laboratories combat this contamination in the pumicing/polishing areas. Generally a mixture of the pumice powder, an Environmental Protection Agency (EPA) approved disinfectant liquid and water are combined to try to control contamination. However, efficacy data for controllability of microbial contamination by this means is not available. Also, many of these disinfectants are extremely corrosive to the skin and eyes, thus proving hazardous for a polishing material that splatters greatly when applied to a high speed polishing wheel of a lathe. Another problem associated with the incorporation of these liquid disinfectants into the pumice powder is the settling of the pumice powder to the bottom of the pan, in which it is held, resulting from gravitational forces. This results in a separation of germicidal liquid and pumice, promoting increased evaporation of the said liquid, thus reducing the amounts of germicidal volume for treating the contamination. Thus, there is no ability to accurately assure the parts per million (ppm) available germicide in the pumice, disinfectant and water mixture are at germicidal levels at the time of polishing an appliance case. Furthermore, the additions of organic materials from ongoing pumicing/polishing of appliance cases, such as tartar, calculus, saliva, blood, mucous and other proteinaceous soils depletes the availability of active germicide, thus depleting the activity level of the germicidal pumice mixture. A further problem associated with the current techniques for pumicing of cases is the lack of efficiency in the continual weighing, diluting, mixing, and adding of the liquids to the pumice powder prior to pumicing steps.
Clinical studies have shown the existence of microbial contamination in the used pumice medium of dental offices and laboratories to be in excess of a quarter billion cells per gram of pumice: a threatening level for a reservoir of potentially pathogenic organisms.
In short, pumice compositions and pumicing techniques, as currently used in the industry, have many disadvantages which prevent the operator from adhering or complying to current guidelines, recommendations and regulations in the dental community. One major disadvantage of the current compositions and techniques is the inability to effectively control the spread of microbial cross-contamination in the pumicing area. Pumice is generally reused from case to case, transferring germs from one dental prosthesis to another and potentially to the operator and possibly even the patient as well. Another disadvantage is the lack of efficiency in preparing the pumice mixture for performing the current techniques. The current techniques of premixing the pumice and liquid and the cleaning and discarding of used material lend themselves to be cumbersome, inefficient, time consuming and messy as well as a potential biohazard for the operator.